New Pathogen and Insect Discoveries from the New Mexico State University Plant Diagnostic Clinic Natalie Goldberg and Jason French, Extension Plant Sciences

Pecan Bacterial Leaf Scorch Abstract Stem and Bulb Nematode

Xylella fastidiosa The New Mexico State University Plant Diagnostic Clinic (NMSU-PDC) provides diagnostic services Ditylenchus dipsaci for the state of New Mexico and serves as a support lab for the New Mexico Department of Agriculture (NMDA) and the National Plant Diagnostic Network (NPDN). The NMSU-PDC, an integrated clinic, processed over 11,000 disease, insect and plant identification samples between 2010 – 2015. The diagnostic capability of the clinic continues to improve and we now have the ability to offer advanced molecular diagnostics for new and regulatory pathogens. As a result of increased capability, we have identified several new pathogens or host-pathogen combinations, on average 5 per year, in New Mexico and the U.S. since 2010. Among the most interesting include: Bacterial Mosaic of Wheat (Clavibacter michiganensis subsp. tessellarium), Soil-borne Wheat Mosaic Virus (SBWMV), Buckeye Rot of ( nicotianae), bulb rot (Phytophthora nicotianae), Eastern cottonwood trunk rot (Phytophthora riparia), Anthracnose of Sunflower Sprouts and Strawberry (Colletotrichum acutatum), Thousand Cankers Disease (Geosmithia morbida), Goss’s Wilt of Corn (Clavibacter michiganensis subsp. nebraskensis), Phytophthora Blight of Bay Laurel (Phytophthora tropicalis), Late Blight of Tomato (Phytophthora infestans), Stem and Bulb Nematode of Garlic (Ditylenchus dipsaci), Pecan Bacterial Leaf Scorch and Bacterial Leaf Scorch of Shade Trees (Xylella fastidiosa). Several new insect pests have also been identified including: Honey Locust Agrilus (Agrilus difficilis), a close relative of the Emerald Ash Borer, Brown Marmorated Stink Bug (Halyomorpha halys), Bagrada Bug (Bagrada hilaris) and Spotted Wing Dropsophila (Drosophila suzukii). Phytophthora diseases Phytophthora spp.

In July of 2015, a sample submitted from an Arizona pecan orchard tested positive for Xylella fastidiosa. The sample exhibited symptoms of marginal leaf scorch and leaflet These garlic blubs, submitted by an home gardener in April of 2015, were found to be tipburn. Subsequently, the bacterium was confirmed in pecans in New Mexico, California infested with stem and bulb nematode, Ditylenchus dipsaci. The infested plants were and Texas. This is the first confirmation of this disease in pecans outside the Southeastern from one particular in an extensive garden of many and over 1,200 United States. plants. This was the first confirmed occurrence of D. dipsaci on any host in New Mexico.

Bacterial Leaf Scorch of Shade Trees Xylella fastidiosa Anthracnose of Strawberry and Sunflower Colletotrichum acutatum

Three new Phytophthora diseases were confirmed in the clinic over the last few years: P. tropicalis on bay laurel (A), P. nicotianae on onion (B), P. infestans on tomato (C), and P. nicotianae on tomato (D). Flatheaded Locust Borer Agrilus difficilis

After the discovery of Pecan Bacterial Leaf Scorch in New Mexico, a survey for Xylella fastidiosa in landscape and native plants was conducted. In landscape plantings, the Colletotrichum acutatum, the causal agent of anthracnose, has recently been found on bacterium was found in Sycamore (A), Chinquapin Oak (B), Chaste Tree (C), Red Oak, two different hosts in New Mexico. It was found on field grown strawberries (A) and on Crape Myrtle, Rosemary, Ash, and Mexican Elder. In unmanaged ecosystems, the edible sunflower sprouts in a controlled environment (B). bacterium was found in Desert Willow, Mesquite, Apache Plume and Coyote Willow. The bacterium was also found in Salt Cedar, an invasive plant species. A First Detector noticed D-shaped exit holes similar to those caused by Emerald Ash Borer on a tree he presumed to be an ash. He immediately notified the NMSU-PDC. Our entomologist investigated the situation and identified the tree as honey locust and the insect as Flatheaded Locust Borer, a close relative of Emerald Ash Borer.